Mixed borides



Patented Oct. 7, 1952 2,613,154 MIXED commas Harold R. Montgomery, Niagara Falls, Ontario, Canada, assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts.

No Drawing. Application May 18, 195i),

Serial N0. 162,800

12 Claims. (01. 106-43) 1' This invention relates to a composition of matter consisting of a mixture of carbon boride and metal boride in certain proportions and to a method of producing the composition. This application is a continuation in part of my copending application Ser. No. 49,859, filed September 17, 1948, now abandoned.

' One object of the invention is to produce a very hard material, having a hardness exceeding 9 on Mohs scale, and which also has hightensile strength for material of its class; Another object of the invention is to produce a hot molded body of very fine crystal structure, since such fine crystal structure is especially desired in a number of products such as dies, auge tips, gauge blocks, mortars and other products. Another object is to provide a composition which can be synthesized from readily available materials of comparatively low cost. Another object is to produce a composition ashard as boron carbide, as easily moldable and yet havin some superior properties such as increased tensile strength (up to twice that of boron carbide) and of fine crystal structure. Another object is to produce a composition which has great resistance to wear and which will take a high polish. I 1

Another object of the invention is to provide a superior method of obtaining'a homogeneous mixture of carbon boride and metal boride. Another object is to provide a simple and readily controlled process for making many pieces of identical composition. e 1

Another object of the invention is to produce articles of great hardness and comparatively 1 high tensile strength. Another object is to produce articles for varioususes, such as for dies or various kinds, gauge tips, gauge blocks, mortars and sandblast nozzles andthe like which have superior wearing qualities. Another object is to make pieces which can be used for truing grinding wheels. I

Other objects will be in part obvious or in part pointed out hereinafter. M

I can use any metal selected from thegroup consisting of titanium, vanadium, chromium, zirconium, columbium, molybdenum, hafnium, tantalum and tungsten-(woliram).- As an example I will describe the synthesis involving titanium. v

I provide a quantity oititanium powder. This is now readily available on the market so I do not have to describe how the ore-is reduced to make this metal powder. The grit size of the commercially available powder is'of the order of 200 mesh and a typical analysis is as follows:'

TABLE I 'litam'um metal powder Analysis on a dry basis, by weight:

This powder comes mixed with about 15% of water since dry titanium powder explodes with a hot flame when exposed to the air.

I further provide a quantity of boron-rich boron carbide in powder form. This is a solid solution of boron in boron carbide and may be produced as follows: Boron carbide, B40 which is equally truly carbon boride or boride of carbon may be produced in accordance with the synthesis of U. S. Patent No. 1,897,214 using the furnace described in U. 5. Patent No. 2,123,158, both being on inventions of R. R. Ridgway. Tons of such carbon boride are now annually produced by a certain manufacturer and have been for a number of years. The pigs so produced in accordance with the above patents do not turn out to be pure B40 but rather each one contains a quantity of substantially 54C material plusv a quantity of carbon-rich boron carbide and/or a quantity of boron-rich boron carbide.

In practice selected samples of each pig are analyzed and then the purer B40 material is selected by hand sorting since it has a comparatively dull appearance that makes it fairly easy to pick out. The remainder has heretofore been mixed together and sold for such uses as lapping compound and metallurgical additions but there is a surplus of this material (carbon-rich and boron-rich boron carbide). It is thus, to a certain extent, a byproduct material.

On the basis of the analyses of the pigs, which as aforesaid are regularly made, I can readily select those having, besides the high grade boron carbide B40, a remainder which is mostly boronrich boron carbide. This material is selected and analyzed and by selecting a considerable number of lots I have on hand boron-rich boron carbide of various proportions of boron. From these lots it is now possible to make a mixture of powders having, any porportion of boron within the limits of the sample having the most boron on the one hand and pure BiC on the other hand. Pure B'iC analyzes as follows:

TABLE II Theoretical analysis of B40 by weight:

Percent Boron 78.3

Carbon 21.7

Over a number of years, in themaufacture of" boron carbide B40, trying always to make as much of the pure B40 material as possible, the boron-rich boron carbide havingqthe most boronanalyzed about as follows:

TABLE III Analysisof boron-richboroncarbide produced in attempt to makeBiCLi having the most boron by weight:

Per cent Boron 83.0

Carbon 15.5 Unidentified but probably mostly oxygen 1.5

It is thus seen that, proceeding in the'manner indicated, I can have an amount ofboronv between 78.3% and about 84.2%. (based on the total boron and carbon present and-excluding impurities). But I can also make a boron-rich boron carbide according to U. S. Patent No. 2,141,617 to the same R. R; Ridgwayand this has been made having as much as 88%01 boron. Using this latter material and mixing it'with the theoretical proportion of titanium, to react all the boron I can produce a vmixed boride as follows:

TABLE Titanium .boridee-carbon' boride material 'By Vol- By ume. Weight,

Percent TiBg so 72 CB4 v 40. 28

Per cent TiBz 23.2

CB4 66.5 Excess boron 7.6 Fe 0.16 Undetermined, mostly oxygen- 2.54

Per cent Fe 0.16 Undetermined, mostly oxygen 2.60

As a practical matter I prefer the material which is between 10% and 50% by volume TiB2 which is between 16.7% and 64% by weight of TiB'z.

EXAMPLE I As a typical example of the production of this mixed boride of titanium and carbon and specifically for the manufacture of the boride of Table V, I used a boron-rich boron carbide analyzing as follows:

TABLE VI Analysis of a. specific lotoi' boron-rich boron carbide, by, weight;

Per. cent Boron 81.71 Carbon 17 .5; Fe 0.39 Remainder undetermined; 0.36

This had beenerushecl and ball milled-toapan' ticle sizeas follows:

, TABLE-VII Particle size of. material o Table VI, by weight:

' Per cent Smaller than 1 micron; l 1 to 2'microns; 7 2 to 3 micronssnu 14 3 to 5 microns; 24 5 to 8 microns; 45 (Mo 11 micronsr 6 I-also used titaniumpowder of the kind above identified. See Table I.

Taking 951 gramsoithe boron-rich boronicarbide of TableVI andiVIIan-d 351 gramsof wet titanium: powderaof fTab16-.-I:' containing 15%.of

water,v I put it into a mullermixer and mixed the materialforgonezhouru A muller'mixerhas a pan rotating on a verticalaxis-andin the pan is a pair of wheels. together with plowsto stir the material and this type of mixer does a. good job of mixing. A thorough mixingofthe partiticles is important for,the..,a.ttainmentof .maximum strength of the-pieces.

The materialso mixed was. then placed in a graphite mold having,.22mold bores. each one half an inch in diameter, and each borebein'g equipped with two graphite mold p'lungers, all as illustrated and described in U. Si Patent No. 2,150,884 to R. R. Ridgwayand ELLE. Bailey. The moldso charged-was then-placed-in the furnace of U. S.'Patent'No. 2,125,588-toR;R.Ridgway-and the material was molded at a tempera,- ture of 2200 C. for: half an'hour. with apressure of 2500 poundszperisquare:inch; Afterycooling the mold was removed :fromthe furnace andbroken away from the 22 pieces which were found to have average-cross-bendingstrength of 75,000 pounds to the squareinch. They had. approximately-the samehardness-as molded boron care bide, but the cross-,bending strength. was muchgreater than that of molded boroncarbide which seldom exceeds 40,000. pounds to the square inch. The 'above'can bejv'ari'ed in many details, and any furnace'which will reach the desired temperature and is equipped with pressure apparatus can be used. The ,minimum'temperature useable in any case is'about1900 C. but actually themold plungers move when. the process isabout completed and it is then. thatthe power (for heating) should be turned off. The pressure can be varied, but th'e,'graphite molds will not stand pressures very much higher than 2500 pounds per square inch and 1000 pounds per square inch is the minimum for good pieces. The pressure is mechanical pressure and I do not know, of any upper limit provided the mold will stand it.

EXAMPLE II In another run I used a boron-rich boron carbide as follows:'

TABLE VIII Analysis of a specific lot of boron-rich boron carbide, by weight: A

1 Per cent Boron 82.00 Carbon 17.31 Fe 0.32

Total '....L

Onethousand and twenty grams of this boronrich boron carbide was'mixed with two hundred six grams of. the titanium metal powder of Table I (dry weight but the powder of course was wet) and then this mixture was processed as described in Example I. The resulting pieces of titanium borideecarbon boride analyzed as follows:

TABLE IX EXAMPLE 111 In another run I used a boron-rich boron carbide as follows:

TABLE X Analysis of a specific lot of boron-rich boron carbide, by weight:

, Percent Boron 81.71 Carbon 17.54 Fe 0.39

Total 99.64

.One thousand grams of this boron-rich boron carbide was mixed with six hundred grams of the titanium powder of Table I (dry weight but the powder of course was wet) and then this mixture was processed as described in Example I. The resulting pieces of titanium boride-carbon boride analyzed as follows: I

. TABLE XI Analysis of mixed boride, by weight:

- Per cent 'TiBz 48.1 CB4 50.3 Excess boron nil Undetermined, mostly Fe and oxygen 1.6

v v Per cent B 54.3

C 11.0 Undetermined, mostly Fe and oxygen 1.6

EXAMPLE IV In another run I used the same boron-rich boron carbide as in Example II, see Table VIII. Eleven hundred five grams of this boron-rich boron carbide was mixed with four hundred ninety five grams of the titanium metal powder of Table-I (dry Weight but the powder of course was wetland then this mixture was processed as described in Example I. The resulting piece of titanium boride-carbon boride analyzed as follows:

. w 100.00 EXAMPLE V l 0 In another run I selected two lots of boron-rich boron carbide identified as A and B as follows:

TABLE x111 Analysis of lots A and B of boron-rich boron carbide, by weight:

Percent Percent Example 1. The resulting pieces 'of titanium boride-carbon boride analyzed as follows:

The particle sizes of the boronrich boron car bide powders used in Examples II to V inclusive were of the same order as the sizes of the particles given in the case of Example I. The rods of the mixed boride had cross-bending strength in pounds per square lIlChBJS' in the following table.

TABLE XV Cross Bending Strengtlrin.

I .Pcunds per Pieces Made According ,to Example When using any of the other metals listed herein I aim to produce the same range of percentages by volume, to wit from 10% to 50% of the metal boride by volume in thecombination of metal boride and carbon boride in which the carbon boride is substantially all of theremainder. I can use boron-rich boron carbide such as identified in Table III or in Table VI. Borides of the elements Ti, V, Cr, Zr, Cb, Mo, Hf, Ta and W which have been identified and which can be made in this reaction include: TiBz, VBz, CrBz, ZrBz, CbBz, M0235, HfBz, 'IaBz, WzBs. Any Of these borides can be-synthesized'from boron-rich boron carbide by addingto the boron-rich-boron carbide an amount of the metal to produce the known metal boride leaving little or no excess metal and using all or nearly all of the excess boron over the formula B40 in the boron-rich boron-carbide, and theiresulting productis substantially a mixture of carbon boride CB4 and boride of the metal.

There are other known borides of these elements, for example CrB, MoB, MozB, WB-and W23, but I believe they are not-formed .in my synthesisbecause the metals have such an aflinity for boron that they take as much of it as is not combined in B40 and will also take boron from the compound B40 leaving excess carbon which, however, does not usually appear as graphite but may exist in solution.

Thus to make any one of these mixed borides with from'10% to 50% by volume'of metalboride I make specific gravity calculations and select a boron-rich boron carbide having enough texcess boron which when combined with sufficient metal to make the boride. of. this'metal'willgive me the volume' percent desired. For-example if it be decidedto make a: mixed carbon boride-molybdenumnboride with 30% by volume of molybdenum boride, I first. take therespectiveshecific bOQ'bOIidG' CB i and from these I can calculate theyveight percentages of each which will give volumepercentages of 30-5-70 respectively. The weight percentages now being known,I can calculate7the amount'ro'f. molybdenum and the amount ofboron to makejthe M0235 in 100 grams ofrtheflcombination; From the foregoing it can readily be determined how much percentage of excess .bor'on1there should be in the boron-rich boron carbide to ,be used, YThenby methods already pointed out Imake up a mixture of boronri'chiboron carbidehavingjjust; this percentage of excessboron, The restis merely a matter-of addin th calculated amount ,o mo ybd n m, doing a thorough Job of-- mixing, charging into the graphitef'mold andimolding in the Ridgway pressure'furnace of'Patent No. "2,125,588 as already described in Example I."

;B.ut .asalready pointed ;-,out, every one of the nine metals listed herein has such a strongafflnity for boron that it will rob .boron carbide 34C of some of the boron which of course leaves an excess of carbon, but this carbon does not appear as graphite if it is no more than 2% by weight on the total B4C+C. So therefore, since useful molded products can be made of mixed borides of any rof the metals herein and carbon,v with not more than 2% of excess carbon by weight on the total excess carbon and 34C, I can make these other productshaving excess carbon. Excess boronwill never appear if there is sufficient metal to unite with it and Iprefer that suflicient metalybe provided-:to take upallthe boron beyonjd'BiC, I-Iowever'5%-'b yweight excess boron can be tolerated and'stillnot'greatly diminish the strength of the-{product v Anytwo orinore of the meta ls listed-can' beused in the process Withboro'n carbide B40 with or without excess boron to produce complexes of carbon borideand metal borides and in any case the total metal'boride-shouldbe-between 10% and 5.0% .by' volume of the product. All of the metal borides of the nine metals herein are compatible with eachother. In some cases ternary or quaternaryboroncompounds may result and in other cases, more mixtures "of wborides. Calculations for the manufacture of pieces using more than one metal involve first deciding the respective vol- 111116. percentages of all of the borides, converting these to weight percentages, figuring out the total excess boron wanted, making up a mixture havingsuch excess boron, then-making a-mixture of the metals-by weight to-provide the required amount byweight of each met-al.

'In orderto-ma-ke any of theabove calculationsyno matter how complex, the only informationbesides that already given and the atomic weights which will be found in any chemical handbook, is the specific gravities of the various boridesinvolved. These are: as follows:

Grams per 0.0.

marina Boride, 'liBz Vanadium Boride,-VBz Chromium Boride, CrBz 'Colum'bium Boride, CbB Molybdenum Boridc, M02135 Hafnium Boride, HIB: exists in material reported as ZrBz Tantalum Boride, THBL 12.38 12.

e ecam -a gravitiesofmolybdenum boride MoaBsandzcar- 7.6 relation o'fvthe metals selected to one another will readily be seen'from the following table.

TABLE XVII Metal 32 3; Group 'Iitauium, Ti 22 IV Vanadium, V 23 V Chromium, Cr 24 VI Zirconium, Zr 40 IV Golumbium, Ch. 41 V Molybdenum, Mo. 42 VI Hainium, Hf 72 IV Tantalum, 'la 73 V Tungsten (Wolfram) W 74 VI The nine diilerent metal borides and also carbon boride are all non-valence compounds, but all give distinct X-ray patterns.

Various metal powders other than titanium powder which are available and I can use are as follows:

TABLE XVIII Analysis on a dry basis, by weight:

Tungsten metal powder Garbon, C Sulphur, S. Phosphorus, P Manganese, Mn Oxygen 0.01 -I 0.04. Balance chiefly... Balance chiefly.

Zirconium metal powder Zirconium, Zr 99.5 Remainder undetermined In the above, the material reported as zirconium is probably actually a mixture of zirconium and hafnium in undetermined proportions, but mostly zirconium.

The foregoing Table XVIII is given by way of example of the kind of metal powders available and not by way of limitation. Of course, if as and when purer powders are available, I can use them. I can also use metal powders which are impurer but naturally much if not all of the impurity will be found in the final product. The remainder of the metals (except hafnium) to wit. columbium, molybdenumarid'tantalum are all available in powder form but I do not have analyses thereof. Hafnium is quite similar to zirconium in chemical properties and is usually present in commercial zirconium and compounds thereof and in fact is usually reported as Zr since it is difficult to distinguish it therefrom.

Thus the boride formed of zirconium powder is probably xZrBz+yHfB2 and this is within my invention.

In the cases of any of the mixed borides herein mentioned, having available boron-rich boron carbide with 88% by weight or less of boron, I can make the mixed boride containing as much as by volume metal boride, the remainder substan tially all carbon boride BiC. Furthermore, in all cases I want as much as 10% by volume of the metal boride. In all the embodiments of the invention therefore, the limits of metal boride are between 10% and 50% by volume and in physical characteristics comparable percentages by volume give comparable results with all the materials where comparable percentages by weight in many cases give difierent results.

I have made mixed borides according to the invention of the following systems: TiBz-l-CB; CrBz-I-CBa ZIBz+CB4 0r itzlBz-l-yHfBri-C'Bi M04B5+CB4 TaBz+CB4 W2B5+CB4 v and in no case could carbide in excess of 4% by weight be detected by X-ray analysis. While carbon has a strong afiinity for many metals including those herein listed, boron appears to have a greater afiinity for them. Carbon has a greater affinity for titanium than for iron. I feel able to predict therefore, that in the cases of the following systems:

there will be no very great percentage of metal carbide formed when the material of the system is made in accordance herewith.

Proceeding as in Example I, I have made tungsten boride-carbon boride pieces accordin to the following analysis:

TABLE XIX Analysis of mixed boride By By Weight Volume Percent Perc nt W'...... 65.8 Undetermined 0. 4

Also proceeding as in Example I, I have made molybdenum boride-carbon boride pieces according to the following analysis:

' TABLE xx Analysis of mixed boride By By Weight Volume Percent Percent M0285 3950 20. 2 013.; 54. 0 70. a Undetermined. 5. 9 Carbon (not assigned) 5 30. 50 B 51. 24 C. 12. 43 Fe. Trace Undetermined 5. 83 100.00

eis a-4 To: make :good pieces according: to myinvention :the mixedboride should comprise from 10 to 50% by volume of metal; boride, the'remainder XX-had less than 6% by weight of material other than molybdenum'boride, CB4, uncombined boron and carbon in solid solution;

It will thuszbe seen that there has :been': pro;- vided,according to this invention, compositions; articles and processes in whichathehvarious'objects hereinabove set forthtogetherrwith; many thoroughly practical advantages are I successfully achieved. As various possible embodimentscan be made of the compositions of the above-invention and as theart herein described might be varied in various parts, all without departing; from the scope of the invention, it is to be-understood that all matter hereinbefore setforth: is; to be interpreted as illustrative and not in a.

limiting sense;

I claim: 1; Process of 'making solid articles ofv ,carb'on boride and metal boride which comprises heating to a temperature of at least1900' C1: under .mechanical pressure of atileast, 1000 pounds; to the square men a' mixture of carbon boride, and metal selected from the group consisting of titanium, vanadium, chromium zirconium, columbium, molybdenum, hafnium, tantalum and tungsten and mixtures thereof; the amount of" metal being'suilicient to synthesize with the boron in the carbon borideat least l% and being-in sufficient to synthesize more-than 50% by volume of metal boride selected from the'group consisting of TiBz, VB2, ClBz, ZrBz, Cb'Bi, MdzB, HfBz, TaBz and W2B5 and mixtures thereof, said carbon boride having at least as much boron as is represented by the formula CB4, the amount of boron in the mixture being sufficient and the amount of carbon in-the mixture being limited so that over and: above the carbon in CB4 and in boride selected fromthe aforesaid group there will not be present after the synthesis uncombinedlcarbon in excess of 2% by-weight of the CB4 and such.

excess nor metal carbide in excess of 4% by Weight ofsaid article.

2. A hard refractory homogeneous article of carbon boride and-metal boride comprising from to 50% by volume of metal boride selected from the group consisting of TiBz, VBz, CrBz, ZlBz, CbBz, M02135, HfBz, T332, and W235 and mixtures. thereof, the remainder not over ,6-% ;by

weight of material other than:CB4,. saido article; being free of uncombined.carbornover-2%,-loy,

Weight of the CB4 and uncombined carbon and said article being free of metalIcarbide over 4% by weight of the said'article, uncombinednboroni and carbon in solid solution, with at least 80% by weight of said remainder being carbon boride CB4, said article having been formed by the combined action of heat of at least 1900 C. top temperature and mechanical pressure of at least 1000' pounds to the square inch.

3. Process-of making solid articles of carbon" boride and metal boride which comprises heating to a temperature of at least 1900 C. under, mechanical pressure of at least 1000 pounds to.

the square inch a mixture of carbon boride and zirconium, the amount of zirconium being suffie cient to synthesize with the boron in the carbon boride at least 10% and being insufficient to syn- The/molybdenum boride-carbon boride materiahlof Table thesizemore. than 50%: by volume of zirconium CB4 and such excess nor-metal carbide in excess of 4% by Weight of the article.

4. A hard refractory homogeneous article of carbon boride and zirconium boride comprising from 10% to 50% by volume of zirconium boride ZrB2,,thev remainder not over 6% by weight of material other ,thanzCBauncombined boron and carbon in solid solution,- with at least by weight of said; remainder being carbon boride CB4, said article beingfree of uncombined carbon over 2% by weight of the CB4 and uncombined carbon and said article :being free of metal carbide over 4% by weight of said article, said article having been formed-by the combined action of heat of at least;.l900:'C-. toptemperature and mechanical pressure of at least 1000 pounds to the square inch. I

5. Process of making solid articles of carbon boride and titanium boride which comprises heating to a temperature of at least 1900 C. under mechanical pressure of at least 1000 pounds to the square inch a mixture ofcarbon boride and titanium, the amount of titanium being sufficient'to synthesize with the boron in the carbon boride at least 10 and being insufficient to synthesizemore than 50% by volume of titanium borlde'TiBz, said carbon boride having at least as much boron as is represented by the formula CB4, the amount of boron in the mixture being suflicient and the amount of carbon in the mixture being limited so that over and above the carbon. in- CB4 and in titanium boride TiBz there will not be present after the synthesis uncombined carbonin excess of 2% by weight of the CB4 and such excess nonmetal carbide in excess of 4% by Weight of the solid article.

6. A hardurefractory homogeneous article of carbon boride :and titanium boride comprising from 10% to 50% byvolume of titanium boride TiBz, the remainder not over 6% by weight of material other than CB4, uncombined boron and carbon in solid-solution, with at least 80% by weightoi.saidiremainder being carbon boride CB4, said article being free of uncombined carbon over:2% byweight of the CB; and uncombined carbon and said article being free of metal carpoundsto.:the. squareinch a, mixture of carbon boride and; tantalum; the amount of tantalum beingsufiicien-t'tonsynthesize-with the boron inthe-carbon bor-ideatleastlO and being insufcient .tosynthesize-moregthan 50% by volumeof,

tantalum: boride-,TaBa; said .carbon boride having at least:asmuch-horomas representedby the iormulalCBi; the amount of .boron in the mixture being-sumcientandmhe amount of carbon in themixture' being limited-so that over and above the carbon in CB and in tantalum boride TaBz 13 there will not be present after the synthesis uncombined carbon in excess of 2% by weight of the CB4 and such excess nor metal carbide in excess of 4% by weight of the solid article.

8. A hard refractory homogeneous article of carbon boride and tantalum boride comprising from to 50% by volume of tantalum boride TaBz. the remainder not over 6% by weight of material other than CB4, uncombined boron and carbon in solid solution, with at least 80% by weight of said remainder being carbon boride CB4, said article being free of uncombined carbon over 2% by weight of the CB4 and uncombined carbon and said article being free of metal carbide over 4 by weight of said article, said article having been formed by the combined action of heat of at least 1900 C. top temperature and mechanical pressure of at least 1000 pounds to the square inch.

9. Process of making solid articles of carbon boride and tungsten boride which comprises heating to a temperature of at least 1900" C. under mechanical pressure of at least 1000 pounds to the square inch a mixture of carbon boride and tungsten, the amount of tungsten being sumcient to synthesize with the boron in the carbon boride at least 10% and being insufilcient to synthesize more than 50% by volume of tungsten boride W235, said carbon boride having at least as much boron as is represented by the formula CB4, the amount of boron in the mixture being suflicient and the amount of carbon in the mixture being limited so that over and above the carbon in CB4 and in tungsten boride W2B5 there will not be present after the synthesis uncombined carbon in excess of 2% by weight of the CB4 and such excess nor metal carbide in excess of 4% by weight of the solid article.

10. A hard refractory homogeneous article of carbon boride and tungsten boride comprising from 10% to 50% by volume of tungsten boride W235, the remainder not over 6% by weight of material other than CB4, uncombined boron and carbon in solid solution, with at least 80% by weight of said remainder being carbon boride CB4, said article being free of uncombined carbon over 2% by weight of the CB4 and uncombined carbon and said article being free of metal carbide over 4% by weight of said article, said article having been formed by the combined action 14 of heat of at least 1900 C. top temperature and mechanical pressure of at least 1000 pounds to the square inch.

11. Process of making solid articles of carbon boride and molybdenum boride which comprises heating to a temperature of at least 1900 C. under mechanical pressure of at least 1000 pounds to the square inch a mixture of carbon boride and molybdenum, the amount of molybdenum being sufficient to synthesize with the boron in the carbon boride at least 10% and being insufficient to synthesize more than 50% by volume of molybdenum boride M02B5, said carbon boride having at least as much boron as is represented by the formula CB4, the amount of boron in the mixture being sufficient and the amount of carbon in the mixture being limited so that over and above the carbon in CB4 and in molybdenum boride M02B5 there will not be present after the synthesis uncombined carbon in excess of 2% by weight of the CB4 and such excess nor metal carbide in excess of 4% by weight of the solid article.

12. A hard refractory homogeneous article of carbon boride and molybdenum boride comprising from 10% to 50% by volume of molybdenum boride MoiBs, the remainder not over 6% by weight of material other than CB4, uncombined boron and carbon in solid solution, with at least by weight of said remainder being carbon boride CB4, said article being free of uncombined carbon over 2% by weight of the CB4 and uncombined carbon and said article being free of metal carbide over 4% by weight of said article. said article having been formed by the combined action of heat of at least 1900 C. top temperature and mechanical pressure of at least 1000 pounds to the square inch.

HAROLD R. MONTGOMERY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,585,412 Podszus May 18, 1926 1,897,214 Ridgway Feb. 14, 1933 2,109,246 Boyer et al. Feb. 22, 1938 2,148,040 Schwarzkopf Feb. 21, 1939 

1. PROCESS OF MAKING SOLID ARTICLE OF CARBON BORIDE AND METAL BORIDE WHICH COMPRISES HEATING TO A TEMPERATURE OF AT LEAST 1900* C. UNDER MECHANICAL PRESSURE OF AT LEAST 1000 POUNDS TO THE SQUARE INCH A MIXTURE OF CARBON BORIDE AND METAL SELECTED FROM THE GROUP CONSISTING OF TITANIUM, VANADIUM, CHROMIUM, ZIRCONIUM, COLUMBIUM, MOLYBDENUM, HAFNIUM, TANTALUM AND TUNGSTEN AND MIXTURES THEREOF, THE AMOUNT OF METAL BEING SUFFICIENT TO SYNTHESIZED WITH THE BORON IN THE CARBON BORIDE AT LEAST 10% AND BEING INSUFFICIENT TO SYNTHESIZE MORE THAN 50% BY VOLUME OF METAL BORIDE SELECTED FROM THE GROUP CONSISTING OF TIB2, VB2, CRB2, ZRB2, CBB2, MO2B5, HFB2, TAB2 AND W2B5 AND MIXTURES THEREOF, SAID CARBON BORIDE HAVING AT LEAST AS MUCH BORON AS IS REPRESENTED BY THE FORMULA CB4, THE AMOUNT OF BORON IN THE MIXTURE BEING SUFFICIENT AND THE AMOUNT OF CARBON IN THE MIXTURE BEING LIMITED SO THAT OVER AND ABOVE THE CARBON IN CB4 AND IN BORIDE SELECTED FROM THE AFORESAID GROUP THERE WILL NOT BE PRESENT AFTER THE SYNTHESIS UNCOMBINED CARBON IN EXCESS OF 2% BY WEIGHT OF THE CB4, AND SUCH EXCESS NOR METAL CARBIDE IN EXCESS OF 4% BY WEIGHT OF SAID ARTICLE. 